Probe card alignment

ABSTRACT

An adjustable load transmitter for adjusting an alignment between a probe card and a bridge beam of a wafer prober, where the probe card is separated from the bridge beam by a gap. The adjustable load transmitter located in the gap, the adjustable load transmitter comprising two rotatable plates adapted for transmitting a load via a load transmission path between the bridge beam and the wafer prober and each comprising two flat, non-parallel contact faces. The adjustable load transmitter removes an angular misalignment between the bridge beam and the set of plates by rotating each of the rotatable plates about a pre-determined adjustment angle such that two angles of inclination are adjusted to zero. The adjustable load transmitter establishes the load transmission path by closing a clearance between the bridge beam and the contact face.

BACKGROUND

The present disclosure relates to semiconductor wafer probers, and more specifically, to adjusting an alignment between a probe card and a bridge beam of a wafer prober. This application is a continuation of application Ser. No. 15/649,762 filed on Jul. 14, 2017.

Testing semiconductor wafers includes electrically contacting a number of wafer contacts (e.g., 15,000) with microscopic contact pins. With a typical load of 10 grams (g) per pin, this sums up to transmitting a load of approximately 150 kilograms (kg) between the probe card comprising the contact pins and a rigid bridge beam mechanically coupled to and approximately aligned in parallel with the probe card.

In this common usage scenario, even small misalignments of (sub-)millimeter scale between probe card and bridge beam may cause inaccurate or defective electrical contacts. The external force causes the two members to move relative to each other, such that the gap separating them will get closed. When they come into physical contact with each other, they may move away from the prepared relative orientation and/or may become unable to assume a desired relative orientation for the case that the full load is applied. As a result, a chip which is actually free from defects may get classified as defective due to improper electrical contacting, or it may even get damaged in places where too large a pressure is applied during testing.

Adjusting the probe card and the bridge beam to a suitable, e.g. parallel, alignment is subject to dimensional tolerances. Especially the probe card may feature a local surface structure and/or a large scale misalignment, e.g. due to vertically arranged conducting strips, which prevents a precise relative parallel alignment with the bridge beam.

SUMMARY

It is an objective of the present disclosure to provide for a method for adjusting an alignment between a probe card and a bridge beam of a wafer prober, a device adapted for performing said method, and a wafer prober system allowing for performing the method utilizing the device. Embodiments of the disclosure are given in the dependent claims. Embodiments of the present disclosure can be freely combined with each other if they are not mutually exclusive.

In one aspect, the present disclosure provides for a method for adjusting an alignment between a probe card and a bridge beam of a wafer prober, the probe card being separated from the bridge beam by a gap, the method comprising providing an adjustable load transmitter in the gap. The load transmitter can comprise a set of plates adapted to be received inside the gap. The set of plates can comprise a first rotatable plate and a second rotatable plate. The set of plates can be adapted for transmitting a load via a load transmission path between the bridge beam and the wafer prober. The load transmission path can comprise the first rotatable plate and the second rotatable plate, each of the plates comprising two flat contact faces, the contact faces of the first rotatable plate being non-parallel to each other, the contact faces of the second rotatable plate being non-parallel to each other, and one of the contact faces of the first rotatable plate being in permanent surface contact with one of the contact faces of the second rotatable plate, each of the first rotatable plate and the second rotatable plate being adapted for being rotated relative to each other around one of their respective normal axes. The method can further comprise removing an angular misalignment between the bridge beam and the contact face of the set of plates facing the bridge beam by rotating each of the rotatable plates about a pre-determined adjustment angle around its respective rotational axis. The adjustment angles can be determined such that two angles of inclination, defined in different non-parallel directions between the bridge beam and the contact face of the set of plates facing the bridge beam, are adjusted to zero. The method can further comprise establishing the load transmission path by closing a clearance between the bridge beam and the contact face of the set of plates facing the bridge beam.

In another aspect, the present disclosure provides for an adjustable load transmitter for adjusting an alignment between a probe card and a bridge beam of a wafer prober, the probe card being separated from the bridge beam by a gap, the load transmitter comprising a set of plates adapted to be received inside the gap. The set of plates can comprise a first rotatable plate and a second rotatable plate. The set of plates can be adapted for transmitting a load via a load transmission path between the probe card and the bridge beam. The load transmission path can comprise the first rotatable plate and the second rotatable plate. Each of the plates can comprise two flat contact faces, the contact faces of the first rotatable plate being non-parallel to each other, and the contact faces of the second rotatable plate being non-parallel to each other. One of the contact faces of the first rotatable plate can be in permanent surface contact with one of the contact faces of the second rotatable plate, and each of the first rotatable plate and the second rotatable plate can be adapted for being rotated relative to each other around one of their respective normal axes.

In yet another aspect, the present disclosure provides for a wafer prober system, comprising a probe card, a bridge beam, and an adjustable load transmitter for adjusting an alignment between the probe card and the bridge beam. The probe card can be separated from the bridge beam by a gap. The load transmitter can comprise a set of plates adapted to be received inside the gap. The set of plates can comprise a first rotatable plate and a second rotatable plate. The set of plates can be adapted for transmitting a load via a load transmission path between the probe card and the bridge beam. The load transmission path can comprise the first rotatable plate and the second rotatable plate, each of the plates comprising two flat contact faces, the contact faces of the first rotatable plate being non-parallel to each other, and the contact faces of the second rotatable plate being non-parallel to each other. One of the contact faces of the first rotatable plate can be in permanent surface contact with one of the contact faces of the second rotatable plate, and each of the first rotatable plate and the second rotatable plate can be adapted for being rotated relative to each other around one of their respective normal axes.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the disclosure are explained in greater detail, by way of example only, making reference to the drawings.

FIG. 1 is a schematic cut through a representative set of plates according to some embodiments of the present disclosure.

FIG. 2 is a schematic cut through a right trapezoidal plate according to some embodiments of the present disclosure.

FIG. 3 is a top view of a plate with an inclined surface according to some embodiments of the present disclosure.

FIG. 4 is a diagram illustrating the movement of four points on the inclined surface upon rotation of one plate according to some embodiments of the present disclosure.

FIG. 5A is a diagram illustrating the change of two perpendicular inclination angles upon rotation of one plate according to some embodiments of the present disclosure.

FIG. 5B is a diagram illustrating the change of two perpendicular inclination angles upon rotation of one plate in a different plate configuration according to some embodiments of the present disclosure.

FIG. 6 is a flow diagram illustrating a method for dimensioning a set of plates according to some embodiments of the present disclosure.

FIG. 7A is a schematic cut through a representative set of plates before rotation according to some embodiments of the present disclosure.

FIG. 7B is a schematic cut through a representative set of plates after rotation according to some embodiments of the present disclosure.

FIG. 7C is a schematic cut through a representative set of plates after rotating and shifting according to some embodiments of the present disclosure.

FIG. 8 is a flow diagram illustrating a method for determining adjustment angles which provide for a specified adjustment according to some embodiments of the present disclosure.

FIG. 9 is a diagram visualizing the number of solutions found for providing a specified alignment according to some embodiments of the present disclosure.

FIG. 10 is a flow diagram representing an exemplary method for aligning a probe card with a bridge beam using the adjustable load transmitter according to some embodiments of the present disclosure.

FIG. 11 illustrates the adjustable load transmitter in the context of an exemplary wafer prober system according to some embodiments of the present disclosure.

FIG. 12 is a flow diagram illustrating a method for using an adjustable load transmitter in accordance with some embodiments of the present disclosure.

FIG. 13 illustrates a block diagram of a load transmitter controller in accordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

A load is to be transmitted between two planar members separated by a gap. The relative orientation between the two planar members shall be maintained with a high precision after exerting the planar members to the load.

In the following, embodiments of the present disclosure are discussed with reference to the FIGS. It is understood that the embodiments discussed in the text and shown in the Figs. are only of illustrative nature. A person of ordinary skill in the art will naturally be able to combine, replace, extend, or otherwise vary the disclosed features without departing from the scope and spirit of the present disclosure.

Aspects of the present disclosure provide a method for adjusting an alignment between a probe card and a bridge beam of a wafer prober, where the method utilizes an adjustable load transmitter comprising a set of plates adapted to be received inside a gap separating a first planar member and a second planar member. For reasons of simplicity, the following description mainly refers to embodiments of the disclosure where the set of plates comprises a vertical arrangement or stack of the plates. Such vertical set of plates is adapted for being deployed in a vertical gap between the two planar members facing each other vertically. However, it will naturally occur to a person of ordinary skill in the art that the set of plates can be turned by 90° to convert the vertical arrangement of the plates into a horizontal one, such that the set of plates may likewise be deployed in a horizontal gap separating the two planar members facing each other in a horizontal arrangement. Embodiments of the disclosure comprise the set of plates in an arbitrary arrangement, where the set of plates is stabilized internally, e.g. by a bolt which is received by holes in the plates, as explained further below. Where applicable, descriptions involving a vertically arranged set of plates shall therefore not be construed as imposing a limitation on embodiments of the disclosure.

The method may provide the capability of adjusting a wafer testing probe card and a bridge beam with high precision for transmitting a load between probe card and bridge beam through a load transmission path with a large cross-sectional area. More specifically, the method may reduce the probability of testing a chip with a false negative result due to improper electrical contact between the probe card and the wafer to be tested. Additionally, the method may reduce the probability of damaging a chip due to improper mechanical contact between the probe card and the wafer to be tested. Embodiments of the disclosure may be advantageous compared to e.g. providing a solid plate in the gap, as they provide for adjusting the mechanical support to a desired orientation. Compared to solutions based on adjustment screws, embodiments of the present disclosure may avoid abrasion, such that the adjustability of the setup is maintained even after long times of repeated usage.

The set of plates comprises at least two rotatable plates which are directly contacting each other via one out of two flat contact faces. The plates should be made of any solid material which is incompressible under the load which is expected to be transmitted by the load transmitter during usage. According to some embodiments, the plates are made of metallic material. Metallic materials such as raw metals or metal alloys may provide for a very high load capacity and good machinability combined with a very low compressibility.

According to some embodiments, the plates are cylindrical segments. This may be achieved by machining the plates with a circular cross-section and have the advantage that a constant distance may be kept to horizontally neighboring objects which may hinder the rotation of the plates otherwise. Furthermore, circular plates are best suitable for adding an annular graduation to the perimeter of the rotatable plates.

The planes defining the cylindrical segments may be oriented perpendicularly to the primary axis of the cylinder, which yields a plane parallel plate with a rectangular cross-section, the cross-section being now oriented parallel to the primary axis. However, at least one of the cutting planes may be tilted against the primary axis with an angle between 0° and 90°. Preferably, each moveable plate of the set of plates comprises one flat contact face in a perpendicular orientation to a rotational or primary axis of the plate, and a further flat contact face being in a slanted orientation relative to this axis. This yields a four cornered cross-section parallel to the primary axis where two neighboring angles are right angles and the two remaining angles of said cross-section are not right angles. According to some embodiments, at least one of the rotatable plates has a right trapezoidal cross-section. This may simplify the machining process of the plates compared to cutting them with a slanted face on both sides, and it may also simplify the calculation of adjustment angles, as explained further below, by which the rotatable plates may be rotated in order to achieve a specified alignment of the adjustable load transmitter. If a cylindrical segment plate is implemented with a right trapezoidal cross-section, then one of its contact faces is circular and the other one is elliptical.

It may be beneficial to select the horizontal dimensions, or diameters, of the plates as large as possible, such that the set of plates just fits the horizontal dimensions of the gap without contacting a horizontally neighboring structure of the gap in any adjustment angle which may be selected for the rotational plates and/or for any other configuration of the set of plates which may be prepared using otherwise moveable plates as described further below.

Regardless of its composition and/or configuration, the set of plates shall be adapted for transmitting a load via a load transmission path between the planar members. This is achieved by the plates directly contacting and facing each other via their flat contact faces which are also adapted for contacting the planar members in the same way. The flat contact faces may provide a capability of transmitting the load between the two planar members through a laminar, full surface, or two-dimensional contact area for each interface between two neighboring plates or between one of the outer plates of the set of plates and the respective planar member they may be facing upon being installed in the gap. The load transmission path comprising a two-dimensional cross section along the whole of its length may be not prone for abrasion, while being highly configurable for providing or correcting an alignment between two planar members with a high alignment precision and resolution.

As mentioned above, the set of plates may comprise more plates than the two rotatable plates mentioned before. FIG. 1 shows a schematic section through a set of plates (e.g., set of plates 100, also referred to as an adjustable load transmitter 100 and/or load transmitter 100 herein) comprising four plates, namely a base plate (e.g., base plate 102) shown at the bottom and being in permanent surface contact with a first rotatable plate (e.g., first rotatable plate 104), which is placed in permanent surface contact below a second rotatable plate (e.g., second rotatable plate 106), which in turn is in permanent surface contact below a slide plate (e.g., slide plate 108) forming the top of the stacked set of plates. The base plate is a plane parallel plate, while the two rotatable plates and the slide plate have a right trapezoidal cross-section. Each plate contains a hole (e.g., slot hole 112) located at a central position. The holes are aligned upon each other and receiving a bolt (e.g., bolt 110) with a screw head. The slide plate further comprises a long hole on its upper side which receives the screw head. The hole in the base plate is shown as a blind hole and the bottom of the bolt is contacting the bottom of the blind hole. Overlaid with the FIG. are one angle scale on each of the rotatable plates and one tick mark each on the base plate and the slide plate.

It is understood that embodiments of the disclosure are neither restricted to the setup comprising merely two rotatable plates, as described above, nor to the four plate design depicted in FIG. 1. It may rather be useful or beneficial to implement the set of plates with three plates or even more than four plates, as may be necessary for a particular usage scenario. However, each embodiment should comprise at least the two rotatable plates in order to achieve full angular adjustability in at least two non-parallel directions. In this disclosure, the discussion of the Figs. will mainly focus on embodiments where the set of plates comprises four plates, for reasons of simplicity.

According to embodiments, the set further comprises a base plate, the load transmission path further comprising the base plate, the base plate comprising two flat contact faces, the contact faces of the base plate being parallel to each other, the first rotatable plate being arranged between the base plate and the second rotatable plate. The base plate is preferably implemented as one of the peripheral plates of the set of plates, i.e. it is preferably adapted for contacting one of the planar members with one of its contact faces, as can be seen in FIG. 1.

According to some embodiments, the base plate is adapted for being fixed to the first planar member. According to some embodiments, the providing comprises fixing the base plate to the probe card. This may prevent accidental entrainment or coupling to the movement of any neighboring moveable plate. The fixture of the base plate may be implemented in various known ways, two non-limiting examples being mechanisms involving clamps or screws.

The base plate may further serve the purpose to fill a major part of the vertical space between the two planar members. This may be achieved by increasing or maximizing the thickness of the base plate. A high alignment position may be desirable in particular applications, which may be achieved with embodiments of the disclosure which comprise moveable plates with merely a small slope angle of the slope's contact surface compared to a plane parallel plate. As will be discussed further below, the angular alignment precision increases with decreasing slope angle of the rotatable plates. Therefore, in these usage scenarios, at least the rotational plates may be machined from thin plates, which may be a manufacturing advantage and may increase flexibility of usage by enabling the use of an identical set of rotatable plates for gaps of different sizes, while the base plate may remain the only part which is specific for a particular gap height.

The contact places of the base plate are parallel to each other in order to prevent angular biasing, which would otherwise have to be considered during installation of the lowest transmitter in a gap between two planar members and/or during determining the adjustment angles which are needed to provide a desired alignment.

According to embodiments, the set further comprises a slide plate, the load transmission path further comprising the slide plate, the slide plate comprising two flat contact faces and being shiftable along at least one of its contact faces, the contact faces of the slide plate being non-parallel to each other. According to some embodiments, the set further comprises a slide plate, the load transmission path further comprises the slide plate, the slide plate comprises two flat contact faces and is shiftable along at least one of its contact faces, the contact faces of the slide plate are non-parallel to each other, the providing comprises installing the base plate between the bridge beam and the second rotatable plate, and the establishing comprises shifting the slide plate until one of its contact faces comes into contact with the bridge beam.

A slide plate may provide additional vertical alignment of the load transmitter, especially after completing the angular alignment of the plate stack. With its two non-parallel contact faces, shifting the slide plate along its at least one shiftable contact face may result in a height adjustment of the set of plates. Particularly, the slide plate may be shifted such that a remaining vertical gap height between the uppermost contact face of the set of plates and the second planar member is closed, i.e. the set of plates is brought into physical contact with the second planar member, and thus, with both planar members at the same time. The slide plate may therefore provide the capability of adjusting the vertical dimension of the set of plates independently from the angular adjustment provided by the two rotatable plates. Especially after completion of the angular adjustment utilizing a method according to some embodiments of the disclosure, the height of the set of plates may be adjusted using the slide plate and without influencing the angular adjustment which may already have been achieved.

Preferably, the slide plate is the plate which is adapted for facing the second planar member, i.e. in a vertically arranged set of plates, the slide plate is preferably the uppermost plate of the set of plates. This may reduce the probability of accidentally moving one or more of the other plates of the set of plates due to frictional coupling, and thus improve the capability to adjust the height of the set of plates and the inclination angles of the set of plates relative to the second planar member independently from each other.

According to some embodiments, the second rotatable plate is arranged between the slide plate and the first rotatable plate. In addition to the shifting degree of freedom, the slide plate may also have a rotational degree of freedom around a rotational axis normal to one of its contact faces. In other words, the slide plate may be one of the rotatable plates, which may allow for designing the load transmitter, e.g. with two or three plates. A load transmitter comprising a rotatable slide plate in a two plate design would then comprise the first rotatable plate and the slide plate being identical with and adapted for acting as the second rotatable plate. A three plate design utilizing a rotatable slide plate might then comprise a base plate according to some embodiments of the disclosure, the first rotatable plate and the slide plate being identical with and adapted for acting as the second rotatable plate. However, decoupling between the degrees of freedom pertaining to vertical and/or angular alignment may be provided by constructing the set of plates with a shift only slide plate. In this case, and as discussed above, it may be advantageous to place the non-rotatable slide plate above the rotatable plates, which would mean that the second rotatable plate is arranged between the slide plate and the first rotatable plate.

The rotatable plates, being adapted for providing angular alignment of the load transmitter, and the slide plate, being adapted for providing additional vertical alignments for the load transmitter, may be considered sufficient for adjusting a sufficiently large number of degrees of freedom of the set of plates in order for utilizing it to act as an adjustable load transmitter. Each degree of freedom of the set of plates may be assigned to a plate comprised by the set of plates for adjusting this degree of freedom, and the entirety of plates configured for adjusting a degree of freedom of the set of plates is referred to as ‘moveable plates’ herein. The top set of moveable plates in the set of plates may be complimented by other, non-moveable plates, which are not adapted for adjusting a degree of freedom of the set of plates. The base plate, as described before and according to some embodiments, is one example, without limitation, of a non-moveable plate. The rotatable plates and the slide plate, as also described above and according to embodiments of the disclosure, are examples, also without limitation, of moveable plates.

According to embodiments, the load transmitter further comprises a bolt, each of the plates comprising a hole, the bolt being received by the holes, at least one of the plates being floatingly supported by the bolt. According to some embodiments, the load transmitter further comprises a bolt, each of the plates comprise a hole, the bolt is received by the holes, an end of the bolt comprises an external thread, the hole of the base plate comprises an internal thread, the internal thread is adapted for receiving the external thread, the plates apart from the base plate are floatingly supported by the bolt, and the method further comprises interlocking the plates by tightening the bolt.

Inserting a bolt through the set of plates may provide additional mechanical stability, e.g. by preventing the plates from slipping off from each other. The holes through the plates are manufactured with clearance relative to the bolts such that the presence of the bolt does not hamper the motion of the moveable plates, e.g. during angular and/or vertical adjustment. The arrangement of plates surrounding the bolt with a clearance is referred to as a ‘floating support’ of the plates by the bolt.

The bolt may act as a guide pin for the plates comprised by the set of plates. This function may be enhanced, i.e. the number of degrees of freedom of the set of plates with respect to the bolt may be further restricted, by providing the bolt with a screw head. The screw head may provide the further advantage of facilitating a tightening of the bolt if at least part of the bolt and a counterpart surface of the holes is provided with a matching pair of threads.

For one of the plates, the hole may be a blind hole, which may prevent an end of the bolt from escaping the set of plates. For the case that the set of plates is a vertical arrangement of plates, the blind hole is preferably comprised by the bottom plate of the set of plates. In embodiments comprising a base plate, the blind hole is preferably comprised by the base plate. The blind hole may comprise an internal thread, and the blind hole and the internal thread may be adapted for receiving a threaded section of the bolt.

According to some embodiments, the base plate comprises a hole, an end of the bolt comprising an external thread, the hole of the base plate comprising an internal thread, the internal thread being adapted for receiving the external thread, the load transmitter being adapted for interlocking the plates by tightening the bolt. This arrangement may be beneficially used for tightening the bolt against the set of plates, which may prevent the plates from slipping off from each other due to the strong static friction thus introduced to the set of plates at the respective contact faces interfacing each other. The static friction may be strong enough that slipping is effectively prevented even if the full load between the two planar members is applied to the load transmitter. In this way, the high adjustment precision which may be provided by the moveable plates may be maintained during load application.

According to some embodiments, the slide plate comprises a hole and can be floatingly supported by the bolt, the hole of the slide plate can be a slot hole.

Providing the slide plate with a slot hole may extend its working range, i.e. the range of vertical positions which can be adjusted using the slide plate, in embodiments where the bolt is used to inhibit lateral movement of the plate. As this restriction may counteract the purpose of the slide plate, the desired function of the slide plate may be restored by providing it with the slot hole, which is preferably oriented in a shifting direction of the slide plate. An example shifting direction of the slide plate is the direction of steepest slope, or largest gradient, of the two contact faces relative to each other. An example shifting direction thus defined is also applicable for embodiments of the load transmitter which are not comprising the bolt.

A further advantage of the bolt may be that it provides for a common rotational axis of the set of plates. This may increase reproducibility and precision of angular adjustments.

According to some embodiments, at least two of the plates are adapted for adhering to each other via magnetic forces. According to some embodiments, the method further comprises adhering at least two of the plates to each other via magnetic forces.

This may prevent the plates from slipping off each other. Such adhesion may be achieved by providing the at least two of the plates, and/or one or more elements, regions, sections, portions, and/or areas etc., of the plates from or with the material (e.g. a ferromagnetic metal such as iron) which is magnetizable and/or susceptible to magnetization by an external magnetic field. The magnetic and/or magnetizable plates may be located at various positions in the set of plates, for instance, in a four plate design, the two inner plates may comprise a permanent source of a magnetic field, while the two outer plates may comprise no such source, but being magnetizable. Another example can use the same configuration as described, but the non-permanent magnetic plates being unsusceptible to a magnetic field. Another example can use the opposite configuration with the magnetic properties of the inner and outer plates interchanged. Another example can use an alternating sequence of a permanent magnetic plate, followed by a non-permanent magnetic or magnetically unsusceptible plate, followed by a permanent magnetic plate, followed by a non-permanent magnetic or magnetically unsusceptible plate. Another example can use a setup comprising three permanent magnetic plates, and/or a setup where all four plates comprised by the set of plates are permanent magnetic or comprise permanent magnetic elements or areas. Analogous considerations apply to embodiments comprising a different number of plates. Permanent magnetization of a plate or an area or element of a plate may be provided by magnetization of the bulk of the plate or its respective magnetized area, or by providing one or more of the magnetic plates with one or more magnetic elements, such as a discreet permanent magnet, which may be in permanent physical connection with the plate or embedded into the bulk of the magnetic plates, a cavity of the magnetic plates, or the like.

According to some embodiments, one or more of the plates are mechanically coupled to motors or drives configured to rotate and/or slide respective plates an appropriate amount.

Before turning to the methods according to embodiments of the disclosure for adjusting an alignment between two planar members, the functionality of the load transmitters is discussed in greater detail in the following, with references being made to the Figs. as appropriate.

An example design for the moveable plates is that of a cylindrical segment, and more preferably, a cylindrical segment where one out of the two cutting planes defining the cylindrical segment is perpendicular to the axis of the cylinder and the other cutting plane is tilted with respect to the cylinder axis. In a schematic cut view of a plane, e.g. oriented parallel to the gradient of the two tilted cutting planes and comprising the primary axis of the cylindrical segment, the cylindrical segment appears as a right trapezoid comprising two right angles on the straightly cut side and two non-right angles on the obliquely cut side, as is shown in FIG. 2. The cylinder sectional plate 200 shown in FIG. 2 can be divided into a straight cylindrical section of diameter D and height h_(min,2) (also referred to as min_h2 in FIG. 2), and a cylindrical wedge of diameter D and height Δ_(h2) (also referred to as delta_h2 in FIG. 2). The straight cylindrical section has a rectangular cross-section, and the cylindrical wedge has a right triangular cross-section. The largest height, or total height h2, of the cylindrical segments plate is the sum of its rectangular height h_(min,2) and its triangular height Δ_(h2) measured in a central gradient plane of the plate. The steepness of the slope provided by the cylindrical segment plate is defined by its slope angle, denoted β₂ (also referred to as angle_2 in FIG. 2). In FIG. 2, which is measured in the central gradient plane as defined before and is representative of the ratio between the largest height difference Δ_(h2) adjustable by moving the plate, and its diameter D, through the relation β2=arctan(Δ_(h2)/D). The equivalent triangle defining this relation is indicated with two dashed lines in FIG. 2.

FIG. 2 illustrates the definition of a ‘thin plate’ as used herein. A thin plate may be a plate with its total height h2 being small (e.g. by an order of magnitude, or a factor of 10 or more) compared to its diameter D. A thin plate may have the advantage of providing a small slope angle, which may analogously be defined using the relationship above with the additional requirement that Δ_(h2) be small, in the same sense as above, compared to the plate diameter D. A plate with a small slope angle may result in a high adjustment precision of the stack of plates relative to the two planar members.

FIG. 3 illustrates a top view of the plate 200 which is shown in a central gradient cut in FIG. 2. The upper contact surface 300 of the plate 200 is drawn with a slightly elliptical shape to illustrate that this surface is tilted against a perpendicular cylindrical cut. An adjustment angle of 0° is indicated on the surface, and four sides of the plate corresponding to adjustment angle positions of 0°, 90°, 180°, and 270° are labeled as side 1 through side 4, respectively. Furthermore, a coordinate system centered at the primary cylindrical axis is overlaid on contact face 300, the x-axis connecting sides 2 and 4 and the y-axis connecting sides 1 and 3, with sides 2 and 3 corresponding to the respective positive hemispheres. Side 2 corresponds to the right hand side in FIG. 2, and side 4 corresponds to the left hand side in FIG. 2. The labels, adjustment angles, and coordinates as well as the relationships between them defined by FIG. 3 will be used in the remaining descriptions of this disclosure.

For the four sides of the plate shown in FIGS. 2 and 3, the respective changes in vertical position in response to adjusting the adjustment angle ω of the plate. The movement of side 1, side 2, side 3 and side 4 is represented by curve 402, 404, 406, and 408, respectively in FIG. 4. FIG. 4 illustrates the changes of vertical positions for these four sides for the scenario that the plate is installed in a set of plates which is pre-set to a configuration where the upper contact face 300 is in a horizontal orientation at adjustment angle ω=0°. The simulation is based on the assumption that the given plate is supported by another cylinder sectional plate, the contact face of which being tilted against horizontality. As a consequence, the upper contact face 300 of the given rotatable plate 200 leaves its horizontal configuration if the adjustment angle ω is changed. At ω=0°, the total height of the set of plates is simulated to be 25 cm. The four curves corresponding to the respective sides of the given plate have sinusoidal shapes with different faces and height offset. Curve 402, representing the vertical position of side 1, is a positive sine with an amplitude of 2.5 cm and an offset of 25 cm. Side 2 is represented by curve 404, which is a negative cosine of the same amplitude and with an offset of 27.5 cm. Curve 406 depicts the vertical position of side 3 by a negative sine of the same amplitude and with offset 25 cm. Eventually, curve 408 represents the change in position of side 4, which is a positive cosine of the same amplitude and with offset 22.5 cm. The four curves shown in FIG. 4 correspond to a plate configuration where both plates have an adjustable height difference Δ_(h) of 2.5 cm. As sides 2 and 4 correspond to the highest and lowest points on contact face 300, respectively, the two adjustable heights sum up to a vertical displacement of +5 cm at ω=180° for side 2, and −5 cm for the lowest point represented by side 4 at the same adjustment angle. Sides 1 and 3 are located at rotationally neutral positions of the given plate and therefore show only the vertical variation of the total height at the respective side caused by the slope of the supporting plate not shown in FIGS. 2 and 3. The simulation is based on the further assumption that the lower contact face of the supporting plate is in a horizontal configuration.

FIG. 5A shows a diagram where the movement of side 2 and side 3 is represented in terms of the inclination angle α measured between the upper contact face 300 of the given plate 200 and a hypothetical horizontal plane. Different from FIG. 4, the simulation of FIG. 5A is based on the assumption that the lower contact face of the given plate 200 is a horizontal configuration. Curve 404 depicts the change of the inclination angle α_(x) measured in positive x-direction (side 2), and curve 406 shows the change in the inclination angle α_(y) measured in positive y-direction (side 3) as defined by the coordinate system shown in FIG. 3. The angle curves of FIG. 5A are equivalent to the height curves 404 and 406, respectively, shown in FIG. 4, i.e. they differ from the respective curves of FIG. 4 only in their amplitude and their ordinate offset, but not in their phase with respect to the adjustment angle ω. For the adjustment angle ω=0°, side 2 is inclined towards horizontality, which corresponds to an inclination angle of α_(x)=1.432°, while the rotationally neutral side 3 has an initial inclination of 0.0°. As the adjustment angle increases towards ω=180°, side 2 equals out at 90° and turns away from horizontality at 180° with an inclination angle of +1.432°. In the same manner, side 3 opens from horizontality towards its minimum inclination angle of α_(y)=−1.432° at ω=90°, and then rising again towards its maximum inclination angle of identical value, but with positive sine, reached at ω=270°. The face difference between sides 2 and 3 of 90° is reflected in the same face difference between curves 404 and 406. For the given plate of FIGS. 2-4 with an adjustable height of 2.5 cm, the inclination angles correspond to a plate with diameter D=100 cm.

FIG. 5B shows a diagram with the inclination angles α_(x) and α_(y) reached by the given plate, with the difference that the lower contact face of the given plate is now supported by a rotational plate which is turned away from the horizontal configuration of FIG. 5A by an adjustment angle ω=217°. The change in rotational configuration introduced different offsets to the two inclination angles, namely an increase of 2.6° on inclination angle α_(x) (represented by curve 404), and an increase of 0.9° for inclination angle α_(y) (represented by curve 406). Comparison of FIGS. 5A and 5B shows that the adjustment of the supporting plate had no effect on the amplitude and phase of the two curves.

The operational principle of the adjustable load transmitter according to embodiments of the disclosure can be demonstrated with an example involving FIGS. 5A and 5B. According to the example, the rotatable plates of the adjustable load transmitter are to be adjusted to unknown adjustment angles such that the set of plates assumes the required inclination angles of α_(x)=+1.2° and α_(y)=+0.9°. It can be seen from FIG. 5A that there is no adjustment angle ω where α_(x) can be adjusted to +1.2° and, at the same time, inclination angle α_(y) has the desired value of +0.9°. Instead, at the two adjustment angles of approximately 150° and 210° where α_(x) reaches a value of +1.2°, α_(y) assumes the values of approximately −0.7° and +0.7°, respectively. However, by turning the supporting plate to the appropriate adjustment angle of ω=217°, the two curves could be shifted upward by two different inclination offsets, and as a result, the desired inclination angles are coincidentally assumed at the adjustment angle ω=0°. In general, a desired inclination angle within the adjustable ranges for α_(x) and α_(y) for a given set of plates may get adjusted by turning each of the rotatable plates about an appropriate adjustment angle, which may be non-zero.

The adjustable range of inclination angles and height differences which can be provided by a given set of plates depends on the dimensions selected for each of the plates in the set. Therefore, the set of plates needs to be dimensioned for a specific or typical environment or usage scenario where the adjustable load transmitter is to be deployed.

According to some embodiments, the method further comprises dimensioning each of the plates such that the thickness of the set of plates is adjustable to match the clearance by rotating the rotatable plates. According to some embodiments, the method further comprises measuring the inclination angles and measuring a length of the clearance. According to some embodiments, the method further comprises using the inclination angles and the dimensions for dimensioning each of the plates such that the thickness of the set of plates is adjustable to match the clearance. The dimensions may comprise, for a given plate, a diameter D, a height offset h_(min), an adjustable height difference Δ_(h), a total height h, and/or a slope angle β as described above. Advantages of dimensioning the set of plates and/or measuring the inclination angles and a length (i.e., in vertical implementation conditions, a height) of the clearance are illustrated by way of the example given in FIG. 6.

FIG. 6 shows a flow diagram for an exemplary method 600 for dimensioning a set of plates according to embodiments of the disclosure. The set of plates in this example comprises a plane parallel base plate, the two rotatable plates supported by the base plate, and a slide plate supported by the second rotatable plate. Although the given example merely refers to a setup with four plates, dimensioning methods 600 may be applied analogously to implementations using a different number of plates, e.g. by repeating a step for a plate of a given type if the particular setup comprises an additional plate of that given type, or by skipping a step for a plate of a given type if the given setup does not comprise a plate of that given type. In the example of FIG. 6, the slide plate is labeled 1, the upper or second rotational plate supporting the slide plate is labeled 2, and the first or lower rotatable plate supporting the first rotatable plate is labeled 3.

At block 602, the target height H is determined which needs to be achieved by the set of plates. The target height H is usually the height of the gap between the two planar members. At block 604, the inclination angles to be adjusted are determined. In the example of FIG. 6, the two different inclination angles are observed in the x and y directions; however, the inclination angles may be observed in two different arbitrary, non-parallel directions. The dimensioning of the plates is then chosen such that the inclination angles to be adjusted are within the adjustable range of inclination angles, which is usually between 0 and the sum of slope angles β of all rotational plates in the set.

At block 606, the slope angle of plate 3 (the lower rotatable plate) is determined first, as this slope angle β₃ defines the largest angular offset which can be added to the adjustable range of the second rotatable plate by setting the adjusted angle of plate 3, as can be seen from the diagrams of FIGS. 5A and 5B. For a given plate diameter D, which is selected to fit the environment where the adjustable load transmitter is to be deployed, the adjustable height difference Δ_(h3) is then selected according to this requirement to yield the slope angle β₃=arctan(Δ_(h3)/D), as can be seen from FIG. 2. The remaining height offset of plate 3, h_(min,3), may then be rounded to the next practical value for manufacturing.

At block 608, the slope angled β₁ for the slide plate and β₂ for the second rotatable plate are chosen. It may be a good choice to select an identical slope angle β₂ to the one chosen for the first rotatable plate in order to align both inclination angles under equivalent conditions. For instance, two rotatable plates with an identical slope angle may introduce identical uncertainties to the adjusted pair of inclination angles. On the other hand, it may be beneficial to manufacture both rotatable plates with different slope angles, e.g. the first rotatable plate with a larger slope angle β₁ and the second rotatable plate with a substantially smaller slope angle β₂. In this case, the rotatable plate with the larger slope angle may be used for course adjustment, while the final fine adjustment may be performed using the rotatable plate with the smaller slope angle. This is, however, at the cost of introducing larger uncertainties to the adjusted inclination angles α₁ and α₂ as the uncertainty of the inclination angles may be a function which grows proportional to a growing slope angle. Uncertainty is a criterion which may be taken into account during dimensioning in general.

Similar considerations as to angular adjustments apply also to the capability of vertical adjustment provided by the slide plate. If the rotatable plates have been chosen with identical slope angles β, the rule of thumb β₁≥2β₃ is suggested to allow for compensating the largest inclination angle which is adjustable by setting the adjustment angles of the rotatable plates. This rule of thumb is, however, not a general rule and the slope angle β₁ may be approximated, simulated, or calculated in a different way which may be more suitable for a given scenario of use.

At block 610, after all slope angles have been defined, the heights are chosen for the different plates, this time including the base plate. For each plate being not plane parallel, this means to select the remaining height offset h_(min), which corresponds to the height of the rectangular part of the cross-section shown in FIG. 2 and sums up to the total plate height h=h_(min)+Δ_(h). For the base plate, this means to select a suitable thickness of a plate from which the base plate is to be manufactured. It may be advantageous, e.g. in order to achieve a more homogeneous waste distribution or to manufacture all plates from the same raw plate, to select an identical value for all total heights h. However, it may also be desirable to distribute the largest part of height difference to the base plate and manufacture the sloped plates as thin and/or light as possible. This may increase flexibility, e.g. by using a thick standard set of sloped plates for several usage scenarios involving pairs of planar members with different gap sizes, and/or minimizing the weight of the moveable plates in order to reduce slipping probability.

As another rule of thumb, the rotatable plates may be chosen with equal total heights h, calculated by (H−h₄)/3, where H is the target height (e.g. the height of the gap), and h4 is the height of the flat plate labeled with 4. Some tolerance or guard bands may be added for convenience. Furthermore, more than one flat plate may be used, e.g. in a modular system, to construct a most suitable combination of flat plates for distributing the gap height into a flat offset section provided by the set of flat plates, and the sloped and/or moveable plates with heights as possibly required otherwise.

At block 612, dimensioning of the set of plates is complete, and a method according to some embodiments of the disclosure may be performed for calculating solutions, i.e. adjustment angles and, optionally, a remaining height difference to be closed by moving the slide plate, for adjusting the moveable plates of an adjustable load transmitter to be manufactured from the previously dimensioned plates to an appropriate set of inclination angles and, optionally, a slide plate position which is expected to provide an alignment according to a particular requirement of inclination angles and target height.

In the following, methods according to embodiments of the disclosure, the methods utilizing the adjustable load transmitter according to embodiments of the disclosure, are discussed with reference to the Figures.

The disclosed method may advantageously provide and utilize the adjustable load transmitter for adjusting an alignment between a first planar member and a second planar member separated from each other by a gap. In particular, the method uses the two rotatable plates to provide angular adjustment between the two planar members by rotating each of the rotatable plates about a pre-determined adjustment angle around its respective rotational axis. The plates are then adjusted further to close a clearance between the second planar member and the contact face of the set of plates facing the second planar member. This way, the method provides for establishing a load transmission path between the planar members. A main advantage may be a beneficial combination of high-precision adjustment and load transmission capability through a load transmission path with a large cross-sectional area.

According to some embodiments, the set further comprises a base plate, the load transmission path further comprises the base plate, the base plate comprises two flat contact faces, the contact faces of the base plate are parallel to each other, and the providing comprises installing the base plate between the first planar member and the first rotatable plate. According to some embodiments, the set further comprises a base plate, the load transmission path further comprises the base plate, the base plate comprises two flat contact faces, the contact faces of the base plate are parallel to each other, and the providing comprises installing the base plate between the probe card and the first rotatable plate. The base plate may serve as a sliding surface for the first rotatable plate. This may have the advantage of reducing abrasion of the first planar member and the first rotatable plate.

FIG. 7A through 7C schematically illustrate the method for a non-limiting example of an adjustable load transmitter according to some embodiments of the disclosure in which the set of plates 100 comprises four plates, namely a plane-parallel base plate 102 supporting the first rotatable plate 104, the first rotatable plate 104 cut straight on one side and slanted on the other side and supporting the second rotatable plate 106, the second rotatable plate 106 cut straight on one side and slanted on the other side and supporting a slide plate 108 cut straight on one side and slanted on the other side. The base plate 102 and the rotatable plates 104, 106 are of equal diameter, while the diameter of the slide plate 108 is slightly larger. The rotatable plates 104, 106 are provided each with an angular scale and the base plate 102 and the slide plate 108 are provided each with a tick mark in a central position.

In FIG. 7A, the rotatable plates 104, 106 are configured in starting positions, defined as the slide plate 108 being shifted such that its tick mark is aligned with the tick mark of the base plate 102, and the rotatable plates 104, 106 being adjusted by an adjustment angle of ω=0° with respect to the respective tick mark. The cut shown in FIGS. 7A-7C is oriented in x direction (connecting sides 2 and 4 as defined in FIG. 3). A required orientation of the second planar member in the x-direction is indicated by a dashed line connecting with the top point of the set of plates 100 in the x-z plane. The upper side of the set of plates 100, i.e. the contact face 300 of the slide plate 108 adapted for facing the second planar member, is tilted against horizontality about the inclination angle α_(x) in x direction. The initial orientation of the interface between the two rotatable plates 104, 106 in x direction is indicated by a coarsely dashed line.

In FIG. 7B, the first rotatable plate 104 is now adjusted to adjustment angle ω₃=32° and the second rotatable plate 106 is adjusted to adjustment angle ω₂=73°. The change in adjustment is also visible by comparison to the coarsely dashed line, which is copied from FIG. 7A. This adjustment was found in this example to result in parallel alignment of contact face 300 to the required alignment in x direction (dashed line). In this example, the angular alignment of contact face 300 is assumed to be also parallel to the required alignment in y direction (not shown). The angular alignment leaves a vertical clearance 700 between contact face 300 and the dashed line representing the required x orientation of the second planar member. In this example, the clearance 700 is also assumed to be parallel to the required alignment in y direction (not shown).

According to some embodiments, the set further comprises a slide plate, the load transmission path further comprises the slide plate, the slide plate comprises two flat contact faces and is shiftable along at least one of its contact faces, the contact faces of the slide plate are non-parallel to each other, the providing comprises installing the slide plate between the second planar member and the second rotatable plate, and the establishing comprises shifting the slide plate until one of its contact faces comes into contact with the second planar member. As indicated by the example given in FIG. 7C, this may yield the advantage of providing vertical adjustment without interfering with the angular adjustment achieved by adjusting the rotatable plates.

In FIG. 7C, the slide plate is shifted towards the right-hand side, such that the clearance 700 is closed. In this example, the clearance 700 is also assumed to be closed in y direction (not shown) as the angular alignment achieved by the adjustments of the rotatable plates 104, 106 is also parallel to the required alignment in y direction. The shift of slide plate 108 results in a parallel transformation of contact face 300 towards the dashed line without changing the angular alignment achieved by the previous adjustment of the rotatable plates 104, 106. The shift of the slide plate 108 completes the discussed adjustments, and as a result, the load transmission path 702 is formed by the intersection of the cross sections of the plates 102, 104, 106, 108 in the adjusted configuration shown in FIG. 7C.

According to some embodiments, the method further comprises dimensioning the set of plates to satisfy, based on expected maximum values for the inclination angles, a largest adjustable height difference in case of the plates with non-parallel contact faces. According to some embodiments, the method further comprises dimensioning the set of plates to satisfy, based on dimensions of the gap, a diameter and a base thickness in case of all the plates.

The method may provide the load transmitter beneficially scaled to the gap size and the typical size of inclination angles to be expected for a given pair of planar members.

According to some embodiments, the method further comprises determining the adjustment angle for each of the rotatable plates based on the inclination angles and on the dimensions of the plates. This may be performed, for instance, by calculating and/or simulating the alignment angles which are realized for each setting (or, alternatively, a particular setting) of the adjustment angles ω. As an advantage, the unknown alignment angles ω needed to bring the adjustable load transmitter into a specific required adjustment may be obtained.

The adjustable load transmitter may be introduced into a wafer prober, as it is commonly used for semiconductor wafer testing, for providing alignment between a probe card and a bridge beam of the wafer prober. In the following, embodiments of the disclosure comprising usage of the adjustable load transmitter according to embodiments of the disclosure are discussed in greater detail. It is understood however that embodiments of the disclosure are not restricted to being used for providing alignment between a probe card and a bridge beam of a wafer prober, as a person of ordinary skill in the art will recognize different usage scenarios where embodiments of the disclosure may be advantageously applied to obtain alignment between two general planar members.

According to some embodiments, the method further comprises determining the dimensions of the gap and the expected maximum values for the inclination angles. According to some embodiments, the method further comprises simulating for a set of load transmitters for multiple adjustment angles the inclination angles that will be adjusted by the rotating of the rotatable plates by the adjustment angles. According to some embodiments, the method further comprises selecting from the set of load transmitters the adjustable load transmitter for which the inclination angles that can be adjusted are larger or equal than the expected maximum values for the inclination angles. According to some embodiments, the method further comprises using the selected adjustable load transmitter for performing the adjusting of the alignment between the probe card and the bridge beam.

Such example methods may advantageously allow for an early verification of the existence of a solution, by simulating the effect of adjusting a given set of plates, before actually selecting and installing a particular load transmitter and performing the adjustment. For wafer testing applications, this may shorten the time from receiving a new probe card to using it for testing.

FIG. 8 shows a flow diagram representing a method 800, based on databases, for determining solutions for a particular adjustment required to be performed. At block 802, a numerical model of the given set of plates is simulated by calculating the inclination angles achieved for a pair of adjustment angles. The results are stored in a first database (“Sim Results DB” in FIG. 8). Upon completion of block 802, the first database comprises all possible solutions, i.e. all inclination angles which can be adjusted with the given set of plates at a pre-determined resolution of adjustment angles.

Blocks 804 and 810 define a loop over a number of desired pairs of inclination angles, wherein each inclination of a desired pair lies within a parameter range of interest. Blocks 806 and 808 are repeated for each desired pair of inclination angles. At block 806, the first database is queried for all adjustment angle pairs which were calculated in steps 802 and 804 to yield the given desired pair of inclination angles. At block 807, being an alternative to block 806, the solutions are calculated directly, i.e. without a simulation. At block 808, each solution thus determined during block 807 or 806 is appended to a second database (“Solutions DB” in FIG. 8) together with the given desired pair of inclination angles the given solution is assigned to. Block 810 determines if any other pairs of inclination angles should be considered.

After completion of the loop, at block 812 a particular pair of inclination angles is determined (e.g. measured) from a given pair of planar members (e.g. the probe card and the bridge beam) for which the alignment is required to be performed. At block 814, the solutions yielding a pair of inclination angles within a user-specified tolerance space (i.e. the space of pairs of inclination angles for which each inclination angle of a given pair lies within the tolerance range around the respective inclination angle of the requested pair) around the requested pair of inclination angles are extracted from the second database. The tolerance space may be selected by a user from a number of accuracy or tolerance categories (e.g. height tolerance +/−1 μm, +/−2 μm, +/−5 μm, +/−10 μm, etc., or inclination angle tolerance +/−0.01°, +/−0.03°, +/−0.05°, +/−0.08°, +/−0.12°, etc.) and is queried from the second database at a given precision.

At block 816, it is checked whether the second database is empty. In case the second database is empty, the required alignment cannot be performed with the given set of plates and a method for mechanical dimensioning of the set of plates according to some embodiments of the disclosure (see FIG. 6 and its discussion) must be repeated (block 818) if an increase of the tolerance space (loosening the filtering conditions, e.g. by selecting the tolerance space with the next larger boundary value) is not an option. If more than one solution exists in the second database, a solution is selected at block 820, for instance by finding the pair of adjustment angles providing the smallest deviation from the required adjustment e.g. in one or both of the inclination angles, in an average value (e.g. arithmetic mean, geometric mean, standard deviation), a vector distance or any other suitable figure of merit derived from the two inclination angles of a given solution. The requested angular adjustment may then be performed with the selected solution according to some embodiments of the disclosure.

It is understood that the determination of solutions for a required pair of inclination angles to be adjusted is not restricted to simulating a numerical model and/or generating solutions databases as described. Rather, it will be clear to a person of ordinary skill in the art that many different approaches may be deployed for this purpose. For instance, the solutions may be directly calculated mathematically, e.g. by finding one or more mathematical equations or functions which allow for determining one or more of the adjustment angles which yield the required inclination angles and/or for determining a space of solutions, and/or by solving a system of equations, etc. In a similar vein, the solutions are not restricted to be stored in and/or queried from a database; they may rather be stored in any other suitable data structure including, for instance, binary computer-readable files, computer-generated and/or manually maintained value tables, and the like.

Now turning to FIG. 9, a diagram is shown where the number of solutions found in the second database obtained for a specific set of plates is encoded by color and/or patterning of a matrix field, where each matrix field corresponds to a queried pair of inclination angles. The displayed ranges of inclination angles are −0.3°≤α_(x)≤+1.5° displayed on the vertical axis and −0.6°≤α_(y)≤+0.6° displayed on the horizontal axis of the diagram. The results summarized in FIG. 9 were simulated for two rotatable plates with dimensions Δh₁=1.2 mm, Δh₂=0.6 mm and D=100 mm (corresponding to slope angles β₁≈0.7° and β₂≈0.34°) and are resolved in categories of resolution 0.1°. The centering of the diagram at α_(x)=0.7° and α_(y)=0.0° corresponds to β₁, in conjunction with the definition of the ω=0° position such that the sloped contact face of plate 1 has no component in y direction at ω=0°. The diagram shows a circular distribution of solutions with a radius β₁≈0.7° around the center of the diagram, which appears elliptical only because the horizontal axis uses a larger scale than the vertical axis. The solutions are distributed around the theoretical 0.7° circle with a torus width of 0.3-0.4°, which corresponds to the second slope angle β₂≈0.34°. The numbers of solutions displayed in FIG. 9 were counted for the tolerance category “+/−0.01°” (corresponding to a height tolerance of 14 μm) for both inclination angles. The diagram shows that e.g. for an operational window of radius 0.3° around a required pair of inclination angles α_(x)=0.0° and α_(y)=0.0° (vertical alignment), there are more than 30 solutions in most categories. On the other hand, there are no solutions for e.g. α_(x)=0.6° and α_(y)=−0.1° as these solutions are out of the specified tolerance category.

FIG. 10 shows a flow diagram illustrating an exemplary adjustment process 1000 which is performed subsequent to the simulation according to some embodiments of the disclosure. The adjustment process illustrated in FIG. 10 applies to a load transmitter comprising two rotatable plates, a slide plate and a threaded bolt floatingly supporting the plates and received by a threaded hole according to embodiments of the disclosure. At block 1002, the solution selected for the alignment (e.g. the solution selected from the second database) is implemented to the plate configuration by adjusting the adjustment angles w to the values of the selected solution. At block 1004, the height of the gap which remains after the angular adjustment (block 1002) is closed by shifting the slide plate accordingly, thus forming the load transmission path. At block 1006, the plates are locked against each other by tightening the bolt against the threaded hole to provide the load transmission path with additional slip protection.

According to some embodiments, the simulating further comprises calculating an uncertainty for each of the inclination angles that will be adjusted, and the selection of the adjustable load transmitter is based on the uncertainties. Uncertainties may be derived, for instance, from dimensional tolerances of plate manufacturing and/or a figure characterizing the imprecision of setting the adjustment angles w. Uncertainties may be used in addition to or instead of the tolerance measures discussed above to define a criterion for selecting the solution to be implemented from the filtered set of solutions which was collected e.g. in the second database. Tracking uncertainties for the inclination angles may be beneficial to obtain a more robust adjustment which is selected based on empirical data instead of or in addition to pure simulation results.

According to some embodiments, the load transmitter being selected from the set is the load transmitter for which the expected maximum values for the inclination angles can be adjusted with the smallest uncertainty among the load transmitters for which the expected maximum values for the inclination angles can be adjusted. Selecting plates which minimize the alignment uncertainty of the largest adjustable inclination angles by construction (e.g. by preferring a plate which was manufactured with a more precise machine and/or which features a smaller slope angle) may beneficially reduce the uncertainty for all inclination angles which can be adjusted with such plate.

FIG. 11 shows a schematic cut through an exemplary wafer testing system 1100 comprising a probe card 1102 and a bridge beam 1104. A test contactor or pedestal substrate 1120 is mounted on the front (lower) side of the probe card 1102. A semiconductor wafer 1110 is facing electrical contacts 1122 of the test contactor in an upside-down orientation such that the electrical contacts 1112 of the wafer are opposing the electrical contacts 1122 of test contactor 1120.

An adjustable load transmitter 100 is disposed in the gap between probe card 1102 and bridge beam 1104 on the back (upper) side of the probe card 1102. The load transmitter 100 comprises a base plate 102, a first rotatable plate 104, a second rotatable plate 106, and a slide plate 108 supporting each other in the mentioned order. Each of the plates comprises a hole and a bolt 110 with screw head is received by the holes. The screw head is bedded in a slot hole 112 of slide plate 108. The rotatable plates comprise handles 1106 which allow for manual adjustment of the adjustment angles. The slide plate comprises a hinge 1108 which allows for automatic adjustment of the slide plate.

The adjustable load transmitter 100 may be used as depicted in wafer testing system 1100 illustrated in FIG. 11 to provide high-precision alignment between probe card 1102 and bridge beam 1104 and create a load transmission path (such as load transmission path 702 shown in FIG. 7) with a large cross section to enable a symmetric, uniform contact of electrical contacts 1112 with electrical contacts 1122. An example alignment process for the system shown in FIG. 11 includes angular alignment of the load transmitter 100 by setting the alignment angles using handles 1106, and subsequently, adjusting the vertical position of slide plate 108 using hinge 1108 to close the clearance remaining between load transmitter 100 and bridge beam 1104 after the angular alignment. Screw 110 may be tightened before closing the electrical contacts between test contactor 1120 and wafer 1110 under test by applying a load to the system in order to prevent slipping of the plates 104, 106, 108 relative to each other.

Although not shown in FIG. 11, in some embodiments, the wafer testing system 1100 can further include one or more drives each comprising one or more electrically controllable motors configured to remove an angular misalignment between the bridge beam 1104 and the contact face of the set of plates (e.g., slide plate 108) by rotating each of the rotatable plates about a pre-determined adjustment angle around its respective rotational axis. In some embodiments, the one or more drives function by executing instructions stored as software in a memory of a control computer and executing the instructions by a processor of the control computer to cause the one or more drives to function. In some embodiments, the control computer performs one or more operations in accordance with FIGS. 6, 8, and/or 10. In some embodiments, the control computer performs calculations, simulations, and/or generates graphs in accordance with FIGS. 4, 5A, 5B, and/or 9.

FIG. 12 is a flow diagram representing a method 1200 illustrating an example method for using an adjustable load transmitter in accordance with some embodiments of the present disclosure. The method 1200 is an example method for adjusting an alignment between a probe card and a bridge beam of a wafer prober, where the probe card is separated from the bridge beam by a gap.

In operation 1202 an adjustable load transmitter can be provided in a gap formed between a probe card and a bridge beam. The adjustable load transmitter can include a set of plates adapted to be received inside the gap. The set of plates can include a first rotatable plate and a second rotatable plate. The set of plates can be adapted for transmitting a load via a load transmission path between the bridge beam and the wafer prober. The load transmission path can include the first rotatable plate and the second rotatable plate. Each of the plates can include two flat contact faces. The contact faces of the first rotatable plate can be non-parallel to each other. The contact faces of the second rotatable plate can be non-parallel to each other. One of the contact faces of the first rotatable plate can be in permanent surface contact with one of the contact faces of the second rotatable plate. Each of the first rotatable plate and the second rotatable plate can be adapted for being rotated relative to each other around one of their respective normal axes.

In operation 1204, an angular misalignment between the bridge beam and the contact face of the set of plates facing the bridge beam can be removed by rotating each of the rotatable plates about a pre-determined adjustment angle around its respective rotational axis. The adjustment angles can be determined such that two angles of inclination, defined in different non-parallel directions between the bridge beam and the contact face of the set of plates facing the bridge beam, are adjusted to zero.

In operation 1206, the load transmission path can be established by closing a clearance between the bridge beam and the contact face of the set of plates facing the bridge beam.

Referring now to FIG. 13, illustrated is a block diagram of a load transmitter controller 1300 in accordance with some embodiments of the present disclosure. In some embodiments, load transmitter controller 1300 performs operations in accordance with FIGS. 6, 8, and/or 10. In some embodiments, the method 1300 performs calculations, simulations, and/or generates graphs in accordance with FIGS. 4, 5A, 5B, and/or 9. The load transmitter controller 1300 can include a memory 1325, storage 1330, an interconnect (e.g., BUS) 1320, one or more processors 1305 (also referred to as CPUs 1305 herein), an I/O device interface 1310, I/O devices 1312, and a network interface 1315.

Each CPU 1305 retrieves and executes programming instructions stored in the memory 1325 or storage 1330. The interconnect 1320 is used to move data, such as programming instructions, between the CPUs 1305, I/O device interface 1310, storage 1330, network interface 1315, and memory 1325. The interconnect 1320 can be implemented using one or more busses. The CPUs 1305 can be a single CPU, multiple CPUs, or a single CPU having multiple processing cores in various embodiments. In some embodiments, a processor 1305 can be a digital signal processor (DSP). Memory 1325 is generally included to be representative of a random access memory (e.g., static random access memory (SRAM), dynamic random access memory (DRAM), or Flash). The storage 1330 is generally included to be representative of a non-volatile memory, such as a hard disk drive, solid state device (SSD), removable memory cards, optical storage, or flash memory devices. In an alternative embodiment, the storage 1330 can be replaced by storage area-network (SAN) devices, the cloud, or other devices connected to the data manager 1300 via the I/O devices 1312 or a communication network 1350 via the network interface 1315.

In some embodiments, the memory 1325 stores instructions 1360 and the storage 1330 stores adjustable load transmitter data 1332. However, in various embodiments, the instructions 1360 and the adjustable load transmitter data 1332 are stored partially in memory 1325 and partially in storage 1330, or they are stored entirely in memory 1325 or entirely in storage 1330, or they are accessed over a network 1350 via the network interface 1315.

Adjustable load transmitter data 1332 can comprise angles, diameters, heights, tolerances, algorithms, databases (e.g., a simulation results database and a solution database), graphs (e.g., as shown in FIGS. 4, 5A, 5B, and/or 9), and other information relevant to the adjustable load transmitter.

The instructions 1360 store processor executable instructions for various methods such as the methods shown and described with respect to FIGS. 6, 8, and 10. The instructions can include plate adjustment instructions 1362. Plate adjustment instructions 1362 can include instructions for determining appropriate rotation angles and/or appropriate shifts. Plate adjustment instructions 1362 can further include instructions for rotating and/or shifting one or more plates by an appropriate amount using I/O devices 1312 such as, for example, drives and/or motors.

In various embodiments, the I/O devices 1312 can include an interface capable of presenting information and receiving input. For example, I/O devices 1312 can receive input from a user and present information to a user interacting with load transmitter controller 1300. In some embodiments, I/O devices comprise drives coupled to one or more plates and configured to rotate and/or shift the one or more plates by an appropriate amount (e.g., angle, distance) based on instructions executed by load transmitter controller 1300.

The present invention may be a system, a method, and/or a computer program product at any possible technical detail level of integration. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device.

Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.

These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions. 

What is claimed is:
 1. A method for adjusting an alignment between a probe card and a bridge beam of a wafer prober, the probe card being separated from the bridge beam by a gap, the method comprising: providing an adjustable load transmitter in the gap, the adjustable load transmitter comprising a set of plates adapted to be received inside the gap, the set comprising a first rotatable plate and a second rotatable plate, the set being adapted for transmitting a load via a load transmission path between the bridge beam and the wafer prober, the load transmission path comprising the first rotatable plate and the second rotatable plate, each of the plates comprising two flat contact faces, the contact faces of the first rotatable plate being non-parallel to each other, the contact faces of the second rotatable plate being non-parallel to each other, one of the contact faces of the first rotatable plate being in permanent surface contact with one of the contact faces of the second rotatable plate, each of the first rotatable plate and the second rotatable plate being adapted for being rotated relative to each other around one of their respective normal axes; removing an angular misalignment between the bridge beam and the contact face of the set of plates facing the bridge beam by rotating each of the rotatable plates about a pre-determined adjustment angle around its respective rotational axis, the pre-determined adjustment angles being determined such that two angles of inclination, defined in different non-parallel directions between the bridge beam and the contact face of the set of plates facing the bridge beam, are adjusted to zero; and establishing the load transmission path by closing a clearance between the bridge beam and the contact face of the set of plates facing the bridge beam.
 2. The method of claim 1, further comprising measuring inclination angles and measuring a length of the clearance.
 3. The method of claim 2, further comprising determining the adjustment angle for each of the rotatable plates based on the inclination angles and on the dimensions of the plates.
 4. The method of claim 2, further comprising using the inclination angles and the dimensions of the plates for dimensioning each of the plates such that a thickness of the set of plates is adjustable to match the clearance.
 5. The method of claim 1, further comprising: dimensioning the set of plates to satisfy, based on expected maximum values for inclination angles, a largest adjustable height difference for plates with non-parallel contact faces; and dimensioning the set of plates to satisfy, based on dimensions of the gap, a diameter and a base thickness for all the plates.
 6. The method of claim 1, further comprising: determining the dimensions of the gap and expected maximum values for the inclination angles; simulating, for a set of load transmitters for multiple adjustment angles, the inclination angles that will be adjusted by the rotating of the rotatable plates by the adjustment angles; selecting, from the set of load transmitters, the adjustable load transmitter for which the inclination angles that can be adjusted are larger or equal than the expected maximum values for the inclination angles; and using the selected adjustable load transmitter for performing the adjusting of the alignment between the probe card and the bridge beam.
 7. The method of claim 6, the simulating further comprising calculating an uncertainty for each of the inclination angles that will be adjusted, wherein selecting the adjustable load transmitter is based on the uncertainties.
 8. The method of claim 7, the load transmitter being selected from the set being the load transmitter for which the expected maximum values for the inclination angles can be adjusted with a smallest uncertainty among the load transmitters for which the expected maximum values for the inclination angles can be adjusted.
 9. The method of claim 1, the set further comprising a base plate, the load transmission path further comprising the base plate, the base plate comprising two flat contact faces, the contact faces of the base plate being parallel to each other, the providing comprising installing the base plate between the probe card and the first rotatable plate.
 10. The method of claim 9, the load transmitter further comprising a bolt, each of the plates comprising a hole, the bolt being received by the holes, an end of the bolt comprising an external thread, the hole of the base plate comprising an internal thread, the internal thread being adapted for receiving the external thread, the plates apart from the base plate being floatingly supported by the bolt, the method further comprising interlocking the plates by tightening the bolt.
 11. The method of claim 9, the providing comprising fixing the base plate to the probe card.
 12. The method of claim 1, the set further comprising a slide plate, the load transmission path further comprising the slide plate, the slide plate comprising two flat contact faces and being shiftable along at least one of its contact faces, the contact faces of the slide plate being non-parallel to each other, the providing comprising installing a base plate between the bridge beam and the second rotatable plate, the establishing comprising shifting the slide plate until one of its contact faces comes into contact with the bridge beam.
 13. The method of claim 1, further comprising adhering at least two of the plates to each other via magnetic forces.
 14. The method of claim 1, at least one of the rotatable plates having a right trapezoidal cross section.
 15. The method of claim 1, the plates being made of metallic material. 